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James Evans the mnmlMaker
(@james-evans-the-mnmlmaker)
New Member
Min Temp Error stays even after changing thermistor

I had a print failure that resulted in a large blob of filament around the hot-end. I heated the hot-end to 280C and began removing the blob. In the process I damaged the leads to the thermistor. I saw a small spark. As soon as this happened the min temp error triggered (I think this is expected).

I had a spare hot-end so I changed it out. I turned on the system and the min temp error was still there. Temp for hot-end reads 0C. I reset the system and the same issue remained. If I plug the bed thermistor into the hot-end thermistor location the error goes away. So I think I have a bad thermistor. I have a spare. I plugged it in and I get the min temp error again. So I ordered another. It was delivered today and after plugging it in I still have the same error.

Do I really have 3 bad thermistors or is there something wrong with the board? The thermistor lines are not fused so I don't know what would be bad after a short and it doesn't make sense that the bed thermistor clears the error. By the way all of the new thermistors trigger a min temp bed error if plugged into the bed also.

Posted : 13/06/2021 11:13 pm
James Evans the mnmlMaker
(@james-evans-the-mnmlmaker)
New Member
Topic starter answered:
RE: Min Temp Error stays even after changing thermistor

I edited and recompiled the firmware to use the ambient thermistor connection for the hot-end. This gave me good readings for bed and hot-end but triggered a min-temp ambient error. I am able to move the z-axis up and down with this error but cannot do anything else from the menu. I removed the controller board after this and I can't see any issues with the thermistor connections. I really hate to buy another board if the thermistors are bad. I'll have to dig out my multimeter tomorrow. What should the thermistors read?

Posted : 14/06/2021 2:12 am
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Min Temp Error stays even after changing thermistor

@jwhevans

Hello and welcome to the Prusaforum!

The thermistors should have an internal resistance of about 100 kohms at room temperature of 25 degrees C.. Here is an overview of the 104NT/GT type:

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 14/06/2021 12:19 pm
James Evans the mnmlMaker
(@james-evans-the-mnmlmaker)
New Member
Topic starter answered:
RE: Min Temp Error stays even after changing thermistor

@karl-herbert

Thanks Karl. I measured ~900 kohm this morning on each thermistor. Seems they are bad or not what was advertised. 

Posted : 14/06/2021 12:56 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Min Temp Error stays even after changing thermistor

@james-evans-the-mnmlmaker

At 900kohms, the printer will generate a mintemp error, since you are well below the 10 degree C. limit. It is best to buy an original thermistor from Prusa or E3D.

https://help.prusa3d.com/en/article/mintemp-and-mintemp-bed_2169

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 14/06/2021 1:02 pm
James Evans the mnmlMaker
(@james-evans-the-mnmlmaker)
New Member
Topic starter answered:
RE: Min Temp Error stays even after changing thermistor

Thanks Karl. I will go with a genuine replacement before I go further with the board. 

Posted : 14/06/2021 3:58 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Min Temp Error stays even after changing thermistor

@james-evans-the-mnmlmaker

Hopefully your Einsy board is not defective. In any case, I would recommend you to perform a factory reset and reflash the firmware after installing the thermistor.

good luck 👍 

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 14/06/2021 4:10 pm
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